全文获取类型
收费全文 | 144篇 |
免费 | 21篇 |
国内免费 | 4篇 |
出版年
2022年 | 2篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 5篇 |
2015年 | 4篇 |
2014年 | 2篇 |
2013年 | 7篇 |
2012年 | 9篇 |
2011年 | 7篇 |
2010年 | 5篇 |
2009年 | 11篇 |
2008年 | 6篇 |
2007年 | 10篇 |
2006年 | 8篇 |
2005年 | 4篇 |
2004年 | 8篇 |
2003年 | 8篇 |
2002年 | 1篇 |
2001年 | 6篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1955年 | 1篇 |
1954年 | 4篇 |
1950年 | 1篇 |
1934年 | 1篇 |
1916年 | 1篇 |
1906年 | 1篇 |
1905年 | 1篇 |
排序方式: 共有169条查询结果,搜索用时 15 毫秒
31.
Henk Schat Riet Vooijs Eric Kuiper 《Evolution; international journal of organic evolution》1996,50(5):1888-1895
Heavy metal tolerant Silene vulgaris plants, originating from different metalliferous sites in Germany and one in Ireland, were crossed to each other and to nontolerant plants from a nonmetalliferous site in The Netherlands. Analysis of the crosses suggested that there were two distinct major gene loci for zinc tolerance among a total of five tolerant populations. The tolerance loci for zinc, copper, and cadmium in the Irish plants were shown to be identical with those in the German populations. It is argued that the occurrence of common major genes for tolerance among different geographically isolated populations must have resulted from independent parallel evolution in local nontolerant ancestral populations. Each of the tolerances studied seems to be controlled by only a few specific major genes. 相似文献
32.
Heavy metal-induced accumulation of free proline in a metal-tolerant and a nontolerant ecotype of Silene vulgaris 总被引:7,自引:0,他引:7
Accumulation of free proline in response to Cu, Cd and Zn was studied in nontolerant and metal-tolerant Silene vulgaris (Moench) Garcke. In the nontolerant ecotype these metals induced a massive accumulation of proline, especially in the leaves. When compared at equimolar concentrations in the nutrient solution, Cu was the most effective inducer, followed by Cd and Zn, respectively. However, when compared at equal toxic strength, as estimated from the degree of root growth inhibition, proline accumulation decreased in the order Cd > Zn > Cu. The threshold exposure levels for proline accumulation coincided with the highest no-effect-concentrations for root growth. In the metal-tolerant ecotype the constitutive proline concentration in the leaves was 5 to 6 times higher than in the nontolerant ecotype. Exposure to Cu and Zn, however, was without any effect on the leaf proline concentration, even at exposure levels that caused a 50% root growth inhibition. Only Cd, when present at concentrations above the highest no-effect-concentration for root growth, induced a further increase of the leaf proline content. Reducing transpiration by placing the plants under a transparent polyethylene cover almost completely inhibited proline accumulation, even at metal accumulation rates in the leaves that caused a 10-fold increase of the proline level in leaves of uncovered plants. The results demonstrate that metal-induced proline accumulation depends on the development of a metal-induced water deficit in the leaves. Differential metal-induced proline accumulation in distinctly metal-tolerant ecotypes is a consequence, rather than a cause of differential metal tolerance. 相似文献
33.
Increased resistance to copper-induced damage of the root cell plasmalemma in copper tolerant Silene cucubalus 总被引:6,自引:0,他引:6
C. H. R. De Vos H. Schat M. A. M. De Waal R. Vooijs W. H. O. Ernst 《Physiologia plantarum》1991,82(4):523-528
The relation between copper tolerance and the sensitivity of plants with respect to the effect of copper on the plasmalemma of root cells was studied using plants from one copper sensitive and two copper tolerant populations of Silene cucubalus Wib. In each population, the external copper concentration needed to induce ion leakage (a measure of damage to the permeability barrier) was similar to the highest no-effect-concentration of copper for root growth in that population. At higher concentrations, the degree of root growth inhibition paralleled the rate of ion leakage, the degree of trypan blue staining (a measure of plasmalemma integrity) and the accumulation of lipid peroxidation products. The amount of copper taken up by the plants was inversely related to their level of copper tolerance. Compared to copper sensitive plants, copper tolerant plants showed no increased resistance to either the sulfhydryl reagent N-ethylmaleimide or the free radical-producing compound cumene hydroperoxide.
These results indicate that damage to the permeability barrier of root cells constitutes the primary effect of copper toxicity in both sensitive and tolerant plants, and that copper tolerance is coupled to the ability of the plants to prevent such damage. This ability might depend on exclusion of copper by the root cell plasmalemma. 相似文献
These results indicate that damage to the permeability barrier of root cells constitutes the primary effect of copper toxicity in both sensitive and tolerant plants, and that copper tolerance is coupled to the ability of the plants to prevent such damage. This ability might depend on exclusion of copper by the root cell plasmalemma. 相似文献
34.
35.
Molecular mechanisms of metal hyperaccumulation in plants 总被引:11,自引:1,他引:10
36.
Sargassum hemiphyllum is commonly found in Japan and Korea, with a variety, var. chinense, that is found distributed in the southern Chinese coast. We previously reported distinct genetic differentiation between the two taxa based on the PCR‐RFLP data of plastid RubiscoL‐S spacer. The present study aims at elucidating the phylogeographic pattern of S. hemiphyllum based on more markers in the nuclear and extranuclear genomes, with a view to reveal the occurrence of hybridization. The two allopatrically distributed taxa were found to be genetically distinct in nuclear ITS2, plastidial Rubisco (Rbc) and mitochondrial TrnW_I (Trn) spacers. Their divergence was postulated to be attributable to the vicariant event which resulted from the isolation of the Sea of Japan during the late Miocene (6.58–11.25 Mya). Divergence within both S. hemiphyllum and the chinense variety was observed based on Trn spacer, while the divergence in S. hemiphyllum was further confirmed in Rbc spacer. This divergence appears to correspond to the separation of the Japanese populations between the Sea of Japan and the Pacific that occurred around 0.92–2.88 Mya (the early Pleistocene). The presence of an ITS2 clone resembling var. chinense sequences in a Japanese population of S. hemiphyllum (JpNS) raises the possibility of the introgression of var. chinense individuals into S. hemiphyllum population. Compared to that between S. hemiphyllum and the chinense variety, hybridization among the Japanese and Korean populations of S. hemiphyllum is highly probable as all these individuals share a pool of nuclear ITS2 sequences, possibly attributable to incomplete concerted evolution of ITS2. 相似文献
37.
Many animal lineages exhibit allometry in sexual size dimorphism (SSD), known as ‘Rensch’s rule’. When applied to the interspecific level, this rule states that males are more evolutionary plastic in body size than females and that male‐biased SSD increases with body size. One of the explanations for the occurrence of Rensch’s rule is the differential‐plasticity hypothesis assuming that higher evolutionary plasticity in males is a consequence of larger sensitivity of male growth to environmental cues. We have confirmed the pattern consistent with Rensch’s rule among species of the gecko genus Paroedura and followed the ontogeny of SSD at three constant temperatures in a male‐larger species (Paroedura picta). In this species, males exhibited larger temperature‐induced phenotypic plasticity in final body size than females, and body size and SSD correlated across temperatures. This result supports the differential‐plasticity hypothesis and points to the role phenotypic plasticity plays in generating of evolutionary novelties. 相似文献
38.
The molecular mechanisms by which plants sense their micronutrient status, and adapt to their environment in order to ensure a sufficient micronutrient supply, are poorly understood. Zinc is an essential micronutrient for all living organisms. when facing a shortage in zinc supply, plants adapt by enhancing the zinc uptake capacity. The molecular regulators controlling this adaptation were recently identified. in this mini-review, we highlight recent progress in understanding the adaptation to zinc deficiency in plants and discuss the future challenges to fully unravel its molecular basis.Key words: adaptation, zinc deficiency, biofortification, molecular regulators, plant nutritionIn an increasingly populated world, agricultural production is an essential element of social development. Agriculture is the primary source of all nutrients required for human life, and nutrient sufficiency is the basis for good health and welfare of the human population.1 Soils with zinc deficiency are widespread in the world, affecting large areas of cultivated soils in India, Turkey, China, Brazil and Australia,2,3 making zinc the most common crop micronutrient deficiency.4 In addition, risk of inadequate zinc diet and zinc malnutrition are estimated to affect one-third of the global human population, i.e., around two billion people.5 Most affected are people living in developing countries, where diets are rich in cereal-based foods. Cereal grains are rich in phytate, which is a potent anti-nutrient, limiting micronutrient bioavailability.6 Zinc deficiency in crop production can be easily ameliorated through zinc fertilization, making agronomic biofortification an important strategy,3 however in the poorer regions, the required infrastructure to provide a reliable supply of zinc fertilizers of sufficient quality, is often not available. In those situations, biofortified crops, in which the zinc status of crops is genetically improved by selective breeding or via biotechnology, offer a rural-based intervention that will more likely reach the population.7 Different traits can be targeted to developing such improved crops, such as plant zinc deficiency tolerance, zinc use efficiency and the accumulation of zinc in edible parts. However, insufficient knowledge on the molecular mechanisms and the regulation of the zinc homeostasis network in plants is a serious bottleneck when pursuing zinc biofortification. 相似文献
39.
40.
Bert J. van der Zaal Leon W. Neuteboom Johan E. Pinas Agnes N. Chardonnens Henk Schat Jos A.C. Verkleij Paul J.J. Hooykaas 《Plant physiology》1999,119(3):1047-1056
We describe the isolation of an
Arabidopsis gene that is closely related to the animal
ZnT genes (Zn
transporter). The protein
encoded by the ZAT (Zn transporter of
Arabidopsis thaliana) gene has 398
amino acid residues and is predicted to have six membrane-spanning
domains. To obtain evidence for the postulated function of the
Arabidopsis gene, transgenic plants with the ZAT coding sequence under
control of the cauliflower mosaic virus 35S promoter were analyzed.
Plants obtained with ZAT in the sense orientation exhibited enhanced Zn
resistance and strongly increased Zn content in the roots under high Zn
exposure. Antisense mRNA-producing plants were viable, with a wild-type
level of Zn resistance and content, like plants expressing a truncated
coding sequence lacking the C-terminal cytoplasmic domain of the
protein. The availability of ZAT can lead to a better
understanding of the mechanism of Zn homeostasis and resistance in
plants.Several heavy metals are essential during plant growth and
development, but their excess can easily lead to toxic effects.
Contamination of soils with heavy metals, either by natural causes or
due to pollution, often has pronounced effects on the vegetation,
resulting in the appearance of metallophytes, heavy-metal-tolerant
plants. The precise mechanisms of uptake, transport, and accumulation
of heavy metals in plants are poorly understood, but several genes
likely to be involved in these processes have been described. Recently,
a family of ZIP genes that are expressed in roots upon Zn
deficiency was isolated from Arabidopsis (Grotz et al., 1998). The
proteins encoded by the ZIP genes have eight predicted TM
regions and a high degree of similarity to the ZRT genes
from yeast that are involved in Zn uptake. Expression of the
ZIP genes in yeast conferred Zn-uptake activities to these
cells, demonstrating that they are probably functional homologs of the
yeast ZRT genes (Grotz et al., 1998). The only other
metal-transporting protein recently identified in plants belongs to the
large family of cation-transporting P-type ATPases (Tabata et al.,
1997), but these proteins are structurally very different from the
metal-transporting proteins mentioned above.Recent data have provided more insight into the mechanisms of
heavy-metal tolerance. Metallophytes often exhibit tolerance to several
different heavy metals, but all of these metals need not be present at
toxic levels in their habitat (Schat and ten Bookum, 1992a; Schat and
Vooijs, 1997, and refs. therein; Schat and Verkleij, 1998). Although
such a feature is suggestive of a general mechanism of heavy-metal
tolerance, recent genetic evidence has shown that a number of different
mechanisms must exist, each with its own metal specificity (Schat and
Vooijs, 1997). In Arabidopsis, a plant species with a typical level of
tolerance to heavy metals, it has been demonstrated that the
Cd-sensitive mutants cad1 and cad2 are defective
in the synthesis of the metal-binding compound phytochelatin (Howden et
al., 1995). cad1 plants were only slightly more
sensitive to Cu and Zn, indicating that phytochelatin-mediated
detoxification is not sufficient for Cu and Zn detoxification (Howden
et al., 1995b). Metallothioneins appear to be of major importance for
constitutive Cu tolerance in Arabidopsis (Zhou and Goldsbrough, 1994).Aside from complexation of heavy metals by heavy-metal-binding
proteins, there is evidence that transport-mediated sequestration can
contribute to heavy-metal tolerance. In the Zn-tolerant plant
Silene vulgaris it was shown that Zn transport across the
tonoplast was about 2.5 times higher than in Zn-sensitive plants of the
same species (Verkleij et al., 1998). The ZRC1 gene from the
yeast Saccharomyces cerevisiae encodes a protein with six
putative TM regions; when overexpressed, this gene confers elevated
resistance to Zn and Cd (Kamizono et al., 1989). A structurally very
similar gene, COT1, was later found to be involved in Co
accumulation in yeast (Conklin et al., 1992).Recently, several genes homologous to ZRC1 and
COT1 have been described in mammalian cells. The first gene
discovered, ZnT-1 (Zn transporter
1), was cloned by virtue of its ability to complement a
mutated, Zn-sensitive cell line (Palmiter and Finley, 1995).
Subsequently, ZnT-2 (Palmiter et al., 1996),
ZnT-3 (Wenzel et al., 1997), and ZnT-4 (Huang and
Gitschier, 1997) have been described. The ZnT-1 protein most likely
transports Zn out of the cells (Palmiter and Finley, 1995), whereas
ZnT-2 confers Zn resistance by facilitating vesicular sequestration
(Palmiter et al., 1996a). Other proteins related to yeast ZRC1/COT1 and
mammalian ZnT have been found in several bacteria; for example, the
CzcD protein from Alcaligenes eutrophus might be involved in
Zn efflux (Nies, 1992).A family of proteins with six TM regions thus seems to be involved in
the transport of heavy metals, mostly Zn, thereby conferring enhanced
resistance toward these metals. To our knowledge, no plant homologs of
this rather widespread gene family have yet been described. In this
paper we describe an Arabidopsis cDNA clone encoding a protein closely
related to the ZnT family of mammalian Zn transporters, demonstrating
that plants do contain these types of genes. Experiments were performed
to analyze the functional properties of the gene. We demonstrate that
overexpression of the complete protein-coding domain results in
enhanced Zn resistance and increased accumulation of Zn in the root.
The relevance of these findings is discussed. 相似文献